Organic-inorganic composite lithium supplement agent and preparation method thereof

Abstract

The invention provides an organic-inorganic composite lithium supplement agent and a preparation method thereof, and relates to the technical field of lithium batteries. The organic-inorganic composite lithium supplement agent comprises an inorganic lithium supplement agent and an organic lithium supplement agent; wherein the organic lithium supplement agent is coated on the surface of the inorganic lithium supplement agent to form a coating layer. According to the structure, water and oxygen are effectively isolated through the organic coating layer, and the problem that inorganic materials easily absorb water and lose efficacy is solved; and meanwhile, the inorganic core is used for providing electric conduction and catalytic action, so that the reaction kinetics and lithium supplement efficiency of the organic material are improved. And an organic decomposition product can form a film in situ, and an electrolyte side reaction caused by inorganic residues is inhibited, so that high stability and high electrochemical performance are both considered.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to an organic-inorganic composite lithium replenishing agent and its preparation method. Background Technology

[0002] Lithium-ion batteries, due to their high energy density and long cycle life, have been widely used in mobile electronic devices, electric vehicles, and energy storage systems. With the increasing demands for extended battery life from end-users, developing battery systems with higher energy density has become a core requirement for the industry. However, during the first charge of a lithium-ion battery, the electrolyte undergoes a decomposition reaction on the surfaces of the positive and negative electrodes, forming a solid electrolyte interphase (SEI) film or CEI film. This process inevitably consumes some of the active lithium ions from the positive electrode. Especially for high-specific-capacity electrode materials such as high-nickel ternary cathodes and silicon-carbon anodes, the consumption of active lithium during the first charge is even greater due to their large specific surface area or significant volume expansion effect. This leads to a decrease in the battery's initial coulombic efficiency, causing significant irreversible capacity loss and severely limiting the actual energy density of the battery.

[0003] To address the aforementioned issue of active lithium loss, cathode lithium replenishment technology has become a current research hotspot. This technology involves adding lithium replenishment additives with high irreversible capacity to the cathode electrode, utilizing the additional active lithium source released during the initial charging process to compensate for lithium loss during SEI film formation and subsequent cycling. Existing cathode lithium replenishment agents are mainly divided into two categories: inorganic lithium replenishment agents and organic lithium replenishment agents. Among them, inorganic lithium replenishment agents are mainly represented by lithium-rich transition metal oxides (such as lithium iron phosphate and lithium nickel phosphate); organic lithium replenishment agents are mainly represented by organic lithium salts such as lithium oxalate.

[0004] However, both existing types of lithium replenishing agents have significant drawbacks in practical applications. Inorganic lithium replenishing agents typically have a high residual alkali content on their surface, making them extremely sensitive to moisture and air in the environment. They are prone to absorbing water, deteriorating, and failing, thus requiring extremely stringent dew point control during slurry preparation and electrode coating, increasing processing difficulty and cost. Furthermore, the decomposition products of inorganic lithium replenishing agents after delithiation are usually catalytically active transition metal oxides. These residues continuously catalyze electrolyte decomposition, accelerating the consumption of active lithium and deteriorating the stability of the electrode / electrolyte interface, leading to a decline in battery cycle performance.

[0005] On the other hand, organic lithium replenishers typically have poor electronic conductivity and high oxidation decomposition potentials. In the absence of a catalyst, organic lithium replenishers often fail to decompose completely during charging, leading to low lithium replenishment efficiency. Furthermore, the undecomposed residues, acting as inert components, reduce the battery's energy density. While the kinetic performance can be improved by adding conductive carbon or metal catalysts, this often involves complex coating processes. In conclusion, obtaining a lithium replenishment material that combines excellent environmental stability, high lithium replenishment efficiency, and good interfacial compatibility is a pressing issue in the current lithium-ion battery technology field.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide an organic-inorganic composite lithium replenisher and its preparation method. The composite structure improves environmental stability through organic coating, enhances conductivity and reaction kinetics through inorganic core, and suppresses interfacial side reactions, thereby achieving a synergistic effect of high lithium replenishment efficiency and long cycle life.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides an organic-inorganic composite lithium supplement, comprising an inorganic lithium supplement and an organic lithium supplement; The organic lithium supplement agent coats the surface of the inorganic lithium supplement agent to form a coating layer.

[0009] The organic lithium supplement includes at least one of the compounds represented by the general formula R-SO2Li; Wherein, R is selected from any one of halogen, C1-C5 alkyl, C1-C5 alkoxy, aryl, heteroaryl, silyl or siloxane; the C1-C5 alkyl, C1-C5 alkoxy, aryl, heteroaryl, silyl or siloxane is unsubstituted or substituted by one or more substituents; the substituent is selected from halogen, cyano, alkyl, alkoxy, alkenyl or alkynyl; The organic-inorganic composite lithium supplement also includes a conductive additive; the conductive additive is dispersed in the coating layer and inside the coating layer.

[0010] In an optional embodiment, the inorganic lithium supplement includes at least one of Li2NiO2 and Li5FeO4; Preferably, the surface of the inorganic lithium supplement has a carbon coating layer or no coating layer; Preferably, the inorganic lithium replenishing agent is doped with a metal element or is not doped with a metal element; the metal element includes at least one of Mg, Al and Zr.

[0011] In an optional embodiment, the conductive additive is selected from at least one of conductive carbon black, conductive graphite, carbon nanotubes, graphene, MXene, and carbon fiber; and / or, The organic-inorganic composite lithium supplement also includes a dispersant; the dispersant is selected from at least one of polyethylene glycol and sodium dodecylbenzenesulfonate.

[0012] Secondly, the present invention provides a method for preparing an organic-inorganic composite lithium supplement as described in any of the foregoing embodiments, wherein the preparation method includes dry mixing and coating or wet mixing and coating.

[0013] In an optional implementation, the dry mixing coating includes: Inorganic lithium supplement, organic lithium supplement and dispersant are mixed and stirred at 2000 rpm to 3000 rpm for 20 min to 30 min to obtain premixed material; Add a conductive additive to the premixed material, and ball mill it at 300 rpm to 400 rpm for 1 to 2 hours under vacuum or inert atmosphere. Then, heat it to 50°C to 100°C and ball mill it at 500 rpm to 800 rpm for 2 to 4 hours. After sieving, obtain the organic-inorganic composite lithium supplement.

[0014] In an optional embodiment, the wet mixing coating includes: Organic lithium supplements and dispersants are dissolved in a solvent to form an organic lithium supplement solution; An inorganic lithium supplement and a conductive additive are added to the organic lithium supplement solution, dispersed, and then heated to 50℃~100℃ for 2h~4h to obtain a mixed solution; The mixture is spray-dried to obtain the organic-inorganic composite lithium supplement; wherein the inlet temperature of the spray dryer is 180℃~200℃ and the outlet temperature is 80℃~100℃.

[0015] Thirdly, the present invention provides a positive electrode sheet, comprising a positive electrode active material, a conductive agent, a binder, and an organic-inorganic composite lithium supplement as described in any of the foregoing embodiments; Preferably, the mass ratio of the organic-inorganic composite lithium supplement to the positive electrode active material is (0.001~2):1; Preferably, the positive electrode active material includes at least one of olivine-type structural materials, spinel-type structural materials, or layered oxide positive electrode materials; The general formula of the positive electrode active material includes LiM. z N 1-z PO4, Li 1+x Ni y Mn 2-x-y O4 or Li 1+a Nib Co c M' 1-a-b- c O2; wherein M and N are one of Fe, Mn, Co and Ni respectively; M' is selected from at least one of Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Zn, Ga, Y, Zr, Nb, Mo, Sn, Ba and rare earth elements; 0≤z≤1, 0≤x≤0.5, 0≤y≤0.5, 0≤a≤0.5, 0≤b≤1, 0≤c≤1 and 0≤a+b+c≤1.

[0016] Fourthly, the present invention provides a lithium secondary battery, comprising a separator, an electrolyte, a negative electrode, and a positive electrode as described in the foregoing embodiments.

[0017] Fifthly, the present invention provides an electrical device including a lithium secondary battery as described in the foregoing embodiments.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: By employing a core-shell structure formed by coating an inorganic lithium supplement with an organic lithium supplement, and leveraging the relative stability of the organic lithium supplement to moisture and air, a dense physical barrier is constructed, effectively preventing direct contact between environmental moisture and the highly active inorganic lithium supplement inside. This significantly solves the problem of inorganic lithium supplements easily absorbing water and failing due to high residual alkali content on their surface, greatly improving the material's environmental stability in air and reducing the stringent dew point requirements for electrode processing environments.

[0019] Meanwhile, the internal inorganic lithium replenisher not only serves as a high-capacity active lithium source but also acts as the conductive framework and catalytic center for the organic lithium replenisher. The presence of the inorganic core improves the poor electronic conductivity of the outer organic lithium replenisher and effectively reduces the oxidative decomposition potential of the organic components, promoting their complete reaction during charging. This solves the problems of poor kinetic performance and low lithium replenishment efficiency of single organic lithium replenishers.

[0020] Furthermore, this composite structure exhibits a synergistic effect during the electrochemical reaction. Organic products generated from the preferential or synergistic decomposition of the organic lithium supplement can in situ coat the surface of the residue after delithiation of the inorganic lithium supplement, forming a stable solid electrolyte interfacial film. This in-situ formed protective film effectively blocks the direct contact between the decomposition products of the inorganic lithium supplement (such as transition metal oxides) and the electrolyte, suppressing their catalytic decomposition side reactions on the electrolyte, thereby significantly improving the interfacial stability and cycle life of the battery system. Detailed Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0022] This application provides an organic-inorganic composite lithium supplement, comprising an inorganic lithium supplement and an organic lithium supplement; wherein the organic lithium supplement coats the surface of the inorganic lithium supplement to form a coating layer.

[0023] The aforementioned inorganic lithium replenishing agent (core / matrix) can be an inorganic compound with high lithium content that can release active lithium ions during charging. As the "core" or framework of the composite material, it primarily functions to provide a large amount of active lithium. In this application, it also possesses the functional properties of a "conductive agent" and a "catalyst," utilizing its relatively high conductivity and specific potential characteristics to assist in the decomposition of the external organic layer. Specifically, this type of material can refer to lithium-rich transition metal oxides (such as lithium ferrite, lithium nickel oxide, etc.), which have high irreversible capacity.

[0024] The aforementioned organic lithium supplements (shell / coating layer) refer to organic lithium salts or organic complexes that possess lithium-supplementing activity (containing lithium) and are relatively stable to environmental moisture and air. They serve as the "outer shell" or coating layer of composite materials. They not only provide active lithium themselves, but more importantly, they act as a physical shield and modify the interface.

[0025] The core feature of the aforementioned lithium supplement lies in the fact that "the organic lithium supplement coats the surface of the inorganic lithium supplement, forming a coating layer." This structural feature indicates that the organic lithium supplement is spatially located on the periphery of the inorganic lithium supplement, forming a continuous or dense layered structure that encapsulates the inorganic lithium supplement internally. This structure differs from simple physical mixing; rather, it forms a composite with core-shell characteristics. Through this coating structure, utilizing the hydrophobic or water- and oxygen-stable properties of the organic lithium supplement, the environmentally sensitive (hygroscopic, high residual alkali) inorganic lithium supplement is isolated from the external environment (air, moisture). This design solves the technical problem of "hygroscopic failure" in inorganic materials, making it possible to process this composite material under normal humidity conditions.

[0026] It should be noted that this coating structure is not a simple superposition of the two, but rather based on the following synergistic mechanisms: First, there is the "organic-inorganic protection" mechanism (environmental stability). As mentioned above, the organic layer acts as a "sacrificial layer" or "protective layer," shielding the highly active inorganic lithium salt from moisture erosion, significantly reducing the residual alkali growth rate of the material, and solving the defect of poor environmental stability of inorganic lithium supplements. Second, there is the "inorganic-organic assistance" mechanism (kinetic enhancement). Organic lithium supplements typically suffer from poor conductivity and high decomposition potential. The internal inorganic lithium supplement (usually a lithium-containing transition metal oxide) has better electronic conductivity.

[0027] The inorganic core, acting as a "built-in conductive network" and "catalytic core," reduces the decomposition overpotential of the external organic layer, promoting its complete decomposition during the first charge, thereby solving the problems of poor kinetics and low lithium replenishment efficiency of organic lithium replenishment agents.

[0028] After the battery has been in operation (decomposed), the decomposition products of the organic lithium replenisher (sulfur-containing organics mentioned in the manual) can be deposited in situ to form a stable SEI film composition.

[0029] This in-situ formed film covers the surface of the residue (transition metal oxide) after the decomposition of the inorganic lithium supplement, blocking the contact between the residue and the electrolyte and inhibiting the catalytic decomposition side reaction of the transition metal oxide on the electrolyte.

[0030] In summary, this composite lithium replenisher, through its structural design of an organic layer encapsulating an inorganic core, significantly improves the environmental stability of the inorganic lithium replenisher and reduces processing difficulty by utilizing the organic layer to isolate moisture and air. Furthermore, the inorganic core acts as a conductive agent and catalyst, improving the conductivity and reaction kinetics of the organic layer and enhancing lithium replenishment efficiency. In addition, the decomposition products of the organic layer can in situ encapsulate inorganic residues, preventing them from contacting the electrolyte and effectively inhibiting the catalytic decomposition of the electrolyte by inorganic residues, thus improving the interfacial stability of the battery.

[0031] In some embodiments, the inorganic lithium supplement includes at least one of Li2NiO2 and Li5FeO4.

[0032] The aforementioned Li2NiO2 (dilithium nickel oxide) is a lithium-rich layered transition metal oxide with extremely high theoretical specific capacity (it can provide two active lithium ions).

[0033] The aforementioned Li5FeO4 (pentalithium iron oxide) is a lithium-rich iron oxide with an antifluorite structure, which can provide more active lithium ions (theoretically, it can extract 4 lithium ions).

[0034] As the core active component of the composite material, it is mainly responsible for providing a large number of active lithium ions during the first charging process to compensate for the irreversible lithium loss caused by the formation of the SEI film.

[0035] It should be noted that although these two types of materials have extremely high capacity, they typically have two significant drawbacks: first, they have a high residual alkali content on the surface, making them extremely sensitive to air / moisture (they are prone to failure after absorbing water); second, the products after delithiation (nickel oxides, iron oxides) have a strong catalytic decomposition effect on the electrolyte. The "organic coating layer" provided in this embodiment is a protective layer designed specifically to address these characteristics.

[0036] It should be noted that organic lithium supplements (such as R-SO2Li) have poor conductivity and high decomposition potential. In contrast, the selected Li2NiO2 and Li5FeO4 (especially after carbon coating) exhibit high conductivity. The inorganic material at the core acts as a "current collector" and "catalyst" for the outer organic layer, effectively reducing the overpotential of the organic layer's oxidative decomposition and promoting its complete reaction.

[0037] Furthermore, the surface of the inorganic lithium supplement may have a carbon coating layer or no coating layer.

[0038] In this embodiment, the inorganic lithium supplement can be exposed on its own surface or pre-coated with a carbon layer before being coated by the outer "organic lithium supplement".

[0039] It should be noted that Li2NiO2 and Li5FeO4 themselves have limited electronic conductivity, or their conductivity may decrease during delithiation. The pre-coated carbon layer constructs a built-in electronic conductivity network, which can significantly reduce the contact resistance of inorganic particles. The carbon layer can also act as a buffer layer between the inorganic core and the organic shell, alleviating the stress caused by volume expansion / contraction during charging and discharging, and preventing structural collapse.

[0040] This embodiment improves the utilization and rate performance of the inorganic core, ensuring that the core can still participate efficiently in electrochemical reactions even when encapsulated in an organic layer.

[0041] It should be noted that the oxidation decomposition potential of organic lithium supplements (typically <4.0V) is lower than that of inorganic lithium supplements (typically >4.0V). Therefore, in the initial stage of charging, the outer organic layer decomposes preferentially. The sulfur-containing products generated by the decomposition of organic matter cover the highly active residues (NiO / FeO, etc.) after lithium removal from Li2NiO2 and Li5FeO4 in situ, forming a dense passivation film. This film effectively blocks the contact between the residues and the electrolyte, fundamentally inhibiting the catalytic decomposition of the electrolyte by transition metal oxides, and solving the problem of inorganic lithium supplements degrading battery cycle life.

[0042] Furthermore, the inorganic lithium replenishing agent may be doped with a metal element or not; the metal element includes at least one of Mg, Al and Zr.

[0043] In this embodiment, magnesium (Mg), aluminum (Al), or zirconium (Zr) elements are introduced into the crystal structure of Li₂NiO₂ and Li₅FeO₄ to partially replace the original metal ions. These dopants (Mg, Al, Zr) generally do not participate in electrochemical redox reactions (inert), but act as "pillars" in the crystal lattice. They possess strong chemical bond energies, which can stabilize the crystal structure in the delithiation state. This suppresses lattice collapse and phase transitions in the inorganic lithium replenishing agent during deep delithiation, thereby improving the structural stability and cycle life of the material, and also further reducing the formation rate of residual alkali on the surface.

[0044] In some embodiments, the organic lithium supplement comprises at least one compound of the general formula R-SO2Li; wherein R is selected from any one of halogen, C1-C5 alkyl, C1-C5 alkoxy, aryl, heteroaryl, silyl or siloxane; the C1-C5 alkyl, C1-C5 alkoxy, aryl, heteroaryl, silyl or siloxane is unsubstituted or substituted by one or more substituents; the substituents are selected from halogen, cyano, alkyl, alkoxy, alkenyl and alkyne.

[0045] The aforementioned core component (R-SO2Li) represents organic sulfonyl lithium or sulfinyl lithium salt compounds. Li (lithium) is the active ion source, extracted during the first charge of the battery to compensate for the loss of active lithium; -SO2- (sulfonyl / sulfinyl) represents the polar functional group connecting the organic group and the lithium ion, determining the material's oxidative decomposition potential and the chemical properties of the decomposition products; R (organic group) is the variable part that determines the material's physical properties (such as solubility, film-forming properties, and hydrophobicity).

[0046] In the R group, halogens, such as fluorine (F) and chlorine (Cl), can be introduced as electron-withdrawing groups to adjust the decomposition potential; C1-C5 alkyl / alkoxy groups refer to short-chain saturated hydrocarbons or ether groups with 1-5 carbon atoms (such as methyl, ethyl, and methoxy). These groups usually impart a certain degree of flexibility and organic solvent compatibility to the material; aryl / heteroaryl groups, such as phenyl and pyridyl, can be introduced into a conjugated system to improve the structural stability of the molecule; siloxane groups, containing Si-O bonds, help to form stable interfacial films similar to ceramics or glass. The R group itself can be unsubstituted or modified by functional groups such as halogens (e.g., fluorination to increase stability), cyano (-CN, to increase polarity), and alkene / alkynyl groups (unsaturated bonds, which help with polymerization or film formation).

[0047] As a specific, non-limiting example, the organic lithium supplement R-SO2Li may include, but is not limited to, one or more of the following: lithium methyl sulfinate (CH3SO2Li), lithium trifluoromethyl sulfinate (CF3SO2Li), lithium perfluorobutyl sulfinate (C4F9SO2Li), lithium phenyl sulfinate (Ph-SO2Li), lithium p-tolyl sulfinate (CH3-Ph-SO2Li), lithium 4-fluorophenyl sulfinate (F-Ph-SO2Li), lithium trimethylsilyl sulfinate ((CH3)3Si-SO2Li), lithium triethylsilyl sulfinate ((C2H5)3Si-SO2Li), and lithium vinyl sulfinate (CH2=CH-SO2Li). Among them, lithium sulfinates containing strong electron-withdrawing groups (such as fluorine atoms) generally have higher oxidation stability; while lithium sulfinates containing siloxane groups help to form interface films with higher mechanical strength and ceramic-like properties; lithium sulfinates containing unsaturated bonds (such as vinyl groups) can undergo polymerization reactions during charging to form a denser polymer network.

[0048] It should be noted that R-SO2Li compounds belong to the category of "film-forming additive type" lithium replenishment materials. Under the influence of charging voltage, R-SO2Li undergoes an oxidative decomposition reaction, releasing Li... + Its decomposition produces sulfur-containing organic compounds or inorganic lithium salts (such as Li₂SO₄). x Sulfur-rich components are deposited in situ on the electrode surface. These products form a sulfur-rich solid electrolyte interphase (SEI / CEI) film. This film has good ionic conductivity and electronic insulation, effectively passivating the positive electrode surface and preventing the continuous oxidative decomposition of the electrolyte.

[0049] Compared to the inorganic lithium supplements provided in the aforementioned embodiments (such as Li2NiO2, which is extremely sensitive to water), R-SO2Li-type organic lithium salts generally exhibit relatively good stability to environmental moisture and air (especially when R is a hydrophobic alkyl or aryl group). When it acts as a "coating layer" encapsulating the outer surface of the inorganic core, it forms a physical barrier, blocking water molecules from contacting the highly active inorganic lithium salt inside, thereby solving the problem of "high residual alkali and easy water absorption" in inorganic lithium supplements.

[0050] Furthermore, the products of delithiation from inorganic lithium replenishers (such as transition metal oxides) often possess catalytic activity, accelerating electrolyte decomposition. The organic / inorganic composite film generated by the preferential or simultaneous decomposition of R-SO2Li can tightly cover the surface of these inorganic residues. This is equivalent to putting a "passivation coat" on the decomposed "core," physically isolating the catalytic sites from contact with the electrolyte and significantly improving the battery's cycle life.

[0051] In some embodiments, the organic-inorganic composite lithium supplement further includes conductive additives and dispersants.

[0052] Preferably, the conductive additive is dispersed in the coating layer and inside the coating layer; Preferably, the conductive additive is selected from at least one of conductive carbon black, conductive graphite, carbon nanotubes, graphene, MXene, and carbon fiber; Preferably, the dispersant is selected from at least one of polyethylene glycol and sodium dodecylbenzenesulfonate.

[0053] The aforementioned conductive additives are carbon-based or non-carbon-based materials with high electronic conductivity. These can include conductive materials ranging from zero-dimensional to three-dimensional, such as conductive carbon black (e.g., SP, acetylene black), conductive graphite, carbon nanotubes (CNTs), graphene, MXene (two-dimensional transition metal carbon / nitride), and carbon fibers. Electron transport channels are constructed within the organic coating layer. Since the organic lithium salt (R-SO2Li) provided in the aforementioned embodiments typically has relatively poor electronic conductivity, the addition of conductive additives is to compensate for this shortcoming.

[0054] The aforementioned dispersants refer to surfactants or polymeric compounds that can reduce interfacial tension and prevent particle agglomeration. Specifically, polyethylene glycol (PEG) and sodium dodecylbenzenesulfonate (SDBS) are provided. These are used to assist organic lithium supplements and conductive agents in the uniform distribution on the inorganic core surface during the preparation process (whether dry or wet), ensuring the density and uniformity of the coating layer.

[0055] The phrase "the conductive additive is dispersed in and inside the coating layer" indicates that the conductive additive is not simply coated on the outermost layer, nor does it exist independently in the core; rather, it is embedded within the matrix composed of the organic lithium supplement. That is, the "organic lithium supplement" and the "conductive additive" form an interpenetrating composite shell structure, enveloping the "inorganic lithium supplement" core. This distribution ensures that every micro-region within the organic layer can be connected to the external electrode and the internal conductive inorganic core through a conductive network, eliminating the "dead zone" of electrical isolation.

[0056] In some preferred embodiments of the present invention, the mass ratio of the inorganic lithium supplement to the organic lithium supplement is 70:30 to 95:5. Within this ratio range, the inorganic lithium supplement acts as the "core," providing the main active lithium capacity, while the organic lithium supplement acts as the "shell," providing sufficient thickness and density to isolate moisture. If the content of the organic lithium supplement is too low (e.g., below 5%), it is difficult to form a continuous and dense coating layer, resulting in the inorganic core being exposed and failing to absorb water; if the content of the organic lithium supplement is too high (e.g., above 30%), it will lead to a decrease in the overall lithium content density of the composite material, and an excessively thick organic layer may increase electron transport resistance, affecting rate performance. Therefore, the preferred mass ratio range (e.g., 80:20 to 90:10) can better balance high capacity performance and excellent environmental stability.

[0057] The introduction of these two components significantly enhances the working mechanism of the composite lithium replenisher. Firstly, the three-dimensional conductive network construction mechanism (kinetic improvement) is crucial. It's important to note that simple organic lithium replenishers (such as R-SO2Li) are typically electronic insulators or semiconductors. If the coating is too thick, electrons cannot easily transfer to the interior, hindering the decomposition reaction and resulting in residual active lithium (dead lithium). Conductive additives (such as carbon nanotubes or graphene) construct "microscopic wires" within the organic layer. On one hand, they connect the external positive electrode active material and the current collector; on the other hand, they connect the internally conductive inorganic lithium replenisher (Li2NiO2 / Li5FeO4). This interconnected conductive network significantly reduces the oxidative decomposition overpotential of the organic lithium replenisher, improves reaction kinetics, and ensures complete decomposition of the lithium replenisher during the first charge, thereby greatly improving lithium replenishment efficiency. Secondly, uneven dispersion of the organic lithium replenisher can lead to the exposure of some inorganic cores (water absorption failure) or excessively thick local organic layers (impeding the reaction). The dispersant utilizes the wetting and steric hindrance effects of PEG or SDBS to enable the organic lithium salt to form a continuous, pore-free film and to uniformly disperse the conductive additives without agglomeration, thereby improving the physical density of the coating layer and more effectively isolating air and moisture, further enhancing the environmental stability of the composite material; at the same time, it also ensures the consistency of the electrochemical reaction.

[0058] This application also provides a method for preparing an organic-inorganic composite lithium supplement as described in any of the foregoing embodiments, wherein the preparation method includes dry mixing and coating or wet mixing and coating.

[0059] This embodiment provides a dry mixing and coating process that eliminates the need for liquid solvents, relying entirely on mechanical forces for coating. The process utilizes a high-speed mixer for pre-dispersion and applies strong mechanical forces such as ball milling, shearing, and impact through a planetary ball mill or fusion machine. During high-speed impact and friction, mechanical energy is converted into localized heat. Taking advantage of the relatively low softening point or ductility of the organic lithium supplement, it undergoes plastic deformation and extension on the surface of the harder inorganic lithium supplement particles, ultimately forming a continuous and dense coating layer. Simultaneously, conductive additives (such as carbon nanotubes) are physically pressed into or embedded in the softened organic coating layer under mechanical forces, constructing a stable conductive network. This dry process is simple and efficient, avoiding the energy-intensive steps of solvent recovery and drying. Furthermore, because it is entirely anhydrous and solvent-free, it minimizes the risk of inorganic lithium supplements (such as Li₂NiO₂) coming into contact with moisture or reacting with polar solvents, making it particularly suitable for environmentally sensitive inorganic materials.

[0060] This invention also provides a wet mixing and coating process that utilizes a liquid solvent as a dispersion medium to achieve uniform mixing and coating at the molecular level. The process first utilizes the solubility of the organic lithium supplement in a specific solvent (such as anhydrous ethanol) to prepare a solution, and then uniformly disperses the insoluble inorganic lithium supplement particles and conductive additives within it. After ultrasonic dispersion and heating and stirring (possibly accompanied by in-situ polymerization), the solvent is rapidly evaporated through methods such as spray drying. As the solvent evaporates, the organic lithium supplement precipitates, crystallizes, or polymerizes in situ on the surface of the inorganic particles, forming a uniformly thick and dense shell. Compared to the dry process, the wet process more easily covers the surface of irregularly shaped inorganic particles, and the spray drying process helps to form composite particles with better sphericity, significantly improving the tap density and flowability of the material, thereby obtaining an organic-inorganic composite lithium supplement with excellent coating uniformity.

[0061] In some embodiments, the dry mixing coating includes: The inorganic lithium supplement, organic lithium supplement, and dispersant are mixed and stirred at 2000 rpm to 3000 rpm (e.g., 2000 rpm, 2100 rpm, 2200 rpm, 2300 rpm, 2400 rpm, 2500 rpm, 2600 rpm, 2700 rpm, 2800 rpm, 2900 rpm, or 3000 rpm, etc.) for 20 min to 30 min (e.g., 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, or 30 min, etc.) to obtain a premix. A conductive additive is added to the premixed material. Under vacuum or an inert atmosphere, the mixture is first ball-milled at 300 rpm to 400 rpm (e.g., 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm, or 400 rpm, etc.) for 1 hour to 2 hours (e.g., 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, or 2.0 h, etc.). Then, the temperature is raised to 50°C to 100°C (e.g., 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C). The material is ball-milled at 500 rpm to 800 rpm (e.g., 500 rpm, 530 rpm, 560 rpm, 590 rpm, 600 rpm, 620 rpm, 650 rpm, 680 rpm, 700 rpm, 750 rpm, or 800 rpm, etc.) for 2 to 4 hours (e.g., 2.0 h, 2.2 h, 2.4 h, 2.5 h, 2.6 h, 2.8 h, 3.0 h, 3.2 h, 3.5 h, 3.8 h, or 4.0 h, etc.). After natural cooling, the material is removed and sieved using a 200 to 400 mesh (e.g., 300 mesh) sieve to obtain the organic-inorganic composite lithium supplement. The sieving step can effectively remove coarse agglomerates that may be generated during the preparation process, ensuring that the particle size distribution of the composite lithium supplement particles is uniform (D50 is usually controlled at 3~10μm), which is beneficial to the smoothness of the subsequent positive electrode slurry coating, preventing particle scratches or protrusions on the electrode surface, and ensuring the processing performance and safety performance of the battery.

[0062] In some embodiments, the wet mixing coating includes: Organic lithium supplements and dispersants are dissolved in a solvent to form an organic lithium supplement solution; An inorganic lithium supplement and a conductive additive are added to the organic lithium supplement solution, dispersed, and then heated to 50℃~100℃ (e.g., 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, or 100℃, etc.) and reacted for 2h~4h (e.g., 2.0h, 2.2h, 2.4h, 2.5h, 2.6h, 2.8h, 3.0h, 3.2h, 3.5h, 3.8h, or 4.0h, etc.) to obtain a mixed solution; The mixture is spray-dried to obtain the organic-inorganic composite lithium supplement; wherein the inlet temperature of the spray dryer is 180℃~200℃ (for example, it can be 180℃, 182℃, 184℃, 185℃, 186℃, 188℃, 190℃, 192℃, 195℃, 198℃ or 200℃, etc.), and the outlet temperature is 80℃~100℃ (for example, it can be 80℃, 82℃, 84℃, 85℃, 86℃, 88℃, 90℃, 92℃, 94℃, 96℃, 98℃ or 100℃, etc.).

[0063] This application also provides a positive electrode sheet, comprising a positive electrode active material, a conductive agent, a binder, and an organic-inorganic composite lithium supplement as described in any of the foregoing embodiments.

[0064] Furthermore, the mass ratio of the organic-inorganic composite lithium supplement to the positive electrode active material is (0.001~2):1.

[0065] The aforementioned ratio settings (from 0.1% to 2) reflect the high flexibility of this electrode design to adapt to different battery design requirements: the low ratio range (e.g., 0.001:1) is suitable for systems with high initial efficiency of the negative electrode (e.g., graphite negative electrodes), requiring only a small amount of lithium replenishment to achieve balance. The high ratio range (e.g., 2:1) is suitable for situations with extremely low initial efficiency of the negative electrode (e.g., high-content silicon-based negative electrodes) or for designs specifically for pre-lithiation, where a large amount of lithium replenishment is needed to provide a significant additional lithium source. By adjusting this ratio, the N / P ratio and active lithium balance of the battery can be precisely controlled without significantly reducing the battery's volumetric energy density (due to less residual lithium replenishment), thereby maximizing energy density.

[0066] Furthermore, the positive electrode active material includes at least one of olivine-type structural materials, spinel-type structural materials, or layered oxide positive electrode materials.

[0067] The general formula of the positive electrode active material includes LiM. z N 1-z PO4, Li 1+x Ni y Mn 2-x-y O4 or Li 1+a Ni b Co c M' 1-a-b- cO2; wherein M and N are one of Fe, Mn, Co and Ni respectively; M' is selected from at least one of Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Zn, Ga, Y, Zr, Nb, Mo, Sn, Ba and rare earth elements; 0≤z≤1, 0≤x≤0.5, 0≤y≤0.5, 0≤a≤0.5, 0≤b≤1, 0≤c≤1 and 0≤a+b+c≤1.

[0068] The above-mentioned olivine-type structure (LiM) z N 1-z In lithium iron phosphate (LiFePO4), M and N represent transition metals (Fe, Mn, Co, Ni). The most typical example is lithium iron phosphate (LiFePO4, i.e., M=Fe, z=1). It has a stable structure and good safety, but its initial efficiency is usually low, and it is very necessary to use lithium supplements to improve its actual operating capacity.

[0069] The above spinel-type structure (Li 1+x Ni y Mn 2-x-y O4) can be lithium manganese oxide (LiMn2O4) or lithium nickel manganese oxide (LiNi). 0.5 Mn 1.5 O4). It features high operating voltage and rate capability.

[0070] The above-mentioned layered oxide cathode (Li) 1+a Ni b Co c M' 1-a-b-c O2) is currently the mainstream material for high-energy-density batteries, commonly known as "ternary materials" (NCM or NCA). Here, 'a' represents the degree of lithium richness; 'b' and 'c' represent the ratio of Ni to Co; and 'M' represents the doping element (such as Al, Mg, Zr, etc., used for structural stability). Examples include NCM811 (high-nickel) and NCM523. High-nickel materials have high surface alkalinity and are sensitive to moisture, making them generally incompatible with inorganic lithium replenishing agents (which are also highly alkaline). However, the organic-coated lithium replenishing agent of this invention, due to its hydrophobic shell, can coexist well with high-nickel ternary materials in the slurry without gelation.

[0071] In the microscopic system of the positive electrode sheet, this composite lithium replenishing agent exhibits a significant component synergistic effect: First, addressing the problem of slurry gelation caused by the strong alkalinity of conventional inorganic lithium replenishing agents (such as Li5FeO4), this invention utilizes the surface organic coating layer (R-SO2Li) to effectively isolate the alkaline core, allowing it to be stably dispersed in the slurry like a common conductive agent, avoiding side reactions with the PVDF binder, thereby significantly improving the processing compatibility of the electrode sheet, achieving uniform coating and high peel strength without modifying existing equipment; Second, during the first charge decomposition process, the lithium replenishing agent not only directly compensates for irreversible lithium loss, making the battery discharge capacity significantly closer to the theoretical design value, but its sulfur-containing organic decomposition products can also encapsulate the residue of the lithium replenishing agent itself in situ and diffuse to cover the surface of the adjacent positive electrode active material, assisting in the construction of a more stable CEI (positive electrode electrolyte interface) film. This in-situ formed protective film effectively suppresses the dissolution and side reactions of positive electrode active materials (especially high-voltage ternary materials) under high voltage, and reduces the oxidative decomposition of electrolyte on the positive electrode side, thereby achieving a comprehensive improvement in battery initial efficiency, energy density and long-cycle stability.

[0072] This application also provides a lithium secondary battery, including a separator, an electrolyte, a negative electrode, and a positive electrode as described in the foregoing embodiments.

[0073] This embodiment provides a lithium secondary battery. The core components of the battery include a positive electrode, a negative electrode, a separator placed between the positive and negative electrodes, and an electrolyte filled therein. The positive electrode specifically employs the aforementioned positive electrode structure with high lithium replenishment efficiency and excellent environmental stability, while the negative electrode can be made of graphite, silicon-carbon, silicon-oxygen, lithium metal, or their alloys as active materials. The lithium secondary battery has no limited form, including but not limited to cylindrical, prismatic, pouch (polymer), or coin cell batteries, and is suitable for various electrochemical systems such as liquid lithium-ion batteries, polymer lithium-ion batteries, and semi-solid or solid-state lithium batteries.

[0074] This application also provides an electrical device, including a lithium secondary battery as described in the foregoing embodiments.

[0075] This embodiment also relates to an electrical device equipped with the aforementioned high-performance lithium secondary battery as a power source or energy storage component. The electrical device covers a wide range of applications, including but not limited to: mobile electronic devices (such as smartphones, tablets, laptops, wearable devices, e-book readers, etc.); electric vehicles (such as pure electric vehicles, hybrid electric vehicles, electric bicycles, electric motorcycles, electric balance scooters, etc.); energy storage systems (such as home energy storage power supplies, industrial energy storage power stations, portable outdoor power supplies, etc.); and other power tools that require rechargeable batteries (such as electric drills, chainsaws), smart home products (such as robot vacuum cleaners, smart speakers), and medical devices, etc.

[0076] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0077] Example 1 This embodiment provides an organic-inorganic composite lithium replenishing agent and its preparation method, as well as a positive electrode sheet and a lithium secondary battery containing the lithium replenishing agent.

[0078] 1. Preparation of organic-inorganic composite lithium supplement (dry mixing and coating): (1) Pre-dispersion: Inorganic lithium supplement Li2NiO2 (dilithium nickel oxide, average particle size 5μm), organic lithium supplement Li3 trifluoromethyl sulfinate (CF3SO2Li, a representative of the general formula R-SO2Li), and dispersant polyethylene glycol (PEG-4000) were added to a high-speed mixer at a mass ratio of 85:12:1. The mixture was stirred at high speed at 2500 rpm for 25 min to achieve preliminary dispersion and pre-mixing of the materials using centrifugal force and shear force, resulting in a premixed material.

[0079] (2) Mechanical coating: The premixed materials were transferred to a planetary ball mill jar with heating function, and conductive carbon nanotubes (CNTs) were added at a mass fraction of 2% of the total materials. The ball mill jar was evacuated and filled with argon for protection. First, the mixture was ball-milled at 350 rpm for 1.5 hours to ensure sufficient contact between the components.

[0080] (3) Heating and film formation: Subsequently, the ball mill was heated to 75°C, maintained at this temperature, and the ball milling speed was increased to 650 rpm, and ball milling continued for 3 hours. During this process, the synergistic effect of thermal energy and high-intensity mechanical energy was used to soften and extend the organic lithium supplement on the surface of the inorganic lithium supplement, forming a dense coating layer. At the same time, conductive carbon nanotubes were embedded in the coating layer and inside.

[0081] (4) Post-processing: After the material has cooled naturally, it is taken out and sieved through a 300-mesh sieve to obtain an organic-inorganic composite lithium supplement with a core-shell structure (denoted as S1).

[0082] 2. Preparation of the positive electrode sheet: (1) The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent (Super P), binder (PVDF), and the organic-inorganic composite lithium supplement S1 prepared above are mixed in a mass ratio of 94:3:2:1.

[0083] (2) Add an appropriate amount of N-methylpyrrolidone (NMP) as a solvent and stir evenly to prepare a positive electrode slurry.

[0084] (3) The slurry is evenly coated on the aluminum foil current collector, dried at 120°C, rolled and die-cut to obtain the positive electrode sheet.

[0085] 3. Preparation of lithium secondary batteries: A negative electrode sheet was prepared using graphite as the negative electrode active material.

[0086] Polypropylene (PP) microporous membrane is used as the diaphragm.

[0087] The electrolyte was prepared by dissolving 1.0 M LiPF6 in a mixed solvent of EC:EMC:DEC = 1:1:1 (volume ratio).

[0088] The positive electrode, separator, and negative electrode are wound and assembled, injected with electrolyte and encapsulated. After formation and capacity testing, a lithium secondary battery is obtained.

[0089] Example 2 The only difference between this embodiment and Embodiment 1 is the value of the preparation parameters; the lower end of the main parameter range used in dry mixing and coating is adopted.

[0090] The specific preparation steps are as follows: In step (1), the speed of the high-speed mixer is 2000 rpm and the stirring time is 20 min.

[0091] In step (2), the ball milling speed in the first stage is 300 rpm and the ball milling time is 1 hour.

[0092] In step (3), the heating temperature is 50°C, the ball milling speed in the second stage is 500 rpm, and the ball milling time is 2 hours.

[0093] The remaining raw material types, proportions, and subsequent electrode and battery preparation steps are the same as in Example 1. The resulting composite lithium replenishing agent is denoted as S2.

[0094] Example 3 The only difference between this embodiment and Embodiment 1 is the value of the preparation parameters; the upper end of the main parameter range in the dry mixing and coating method is used.

[0095] The specific preparation steps are as follows: In step (1), the speed of the high-speed mixer is 3000 rpm and the stirring time is 30 min.

[0096] In step (2), the ball milling speed in the first stage is 400 rpm and the ball milling time is 2 hours.

[0097] In step (3), the heating temperature is 100℃, the ball milling speed in the second stage is 800 rpm, and the ball milling time is 4h.

[0098] The remaining raw material types, proportions, and subsequent electrode and battery preparation steps are the same as in Example 1. The resulting composite lithium replenishing agent is designated as S3.

[0099] Example 4 This embodiment uses a wet-process mixing and coating process to prepare an organic-inorganic composite lithium supplement, and adopts the lower end of the main parameter range of the wet process.

[0100] 1. Preparation of organic-inorganic composite lithium supplement (wet mixing and coating): (1) Solution preparation: Dissolve the organic lithium supplement lithium trifluoromethyl sulfinate (CF3SO2Li) and the dispersant sodium dodecylbenzene sulfonate (SDBS) in anhydrous ethanol and stir until completely dissolved to prepare an organic lithium supplement solution with a mass concentration of 5%.

[0101] (2) In-situ composite: Inorganic lithium supplementer Li2NiO2 and conductive agent carbon nanotubes (CNT) were added to the above solution. After ultrasonic dispersion for 30 min, the system was heated to 50 °C and reacted under stirring for 2 h to allow the organic lithium supplementer to be initially adsorbed and polymerized on the surface of inorganic particles.

[0102] (3) Spray drying: The reaction mixture is spray dried. The inlet temperature is set to 180℃ and the outlet temperature is set to 80℃. After the solvent evaporates rapidly, dry powder particles are obtained.

[0103] The types and proportions of the remaining raw materials (converted to dry weight ratio) remained the same as in Example 1. The resulting composite lithium supplement was designated as S4.

[0104] 2. Preparation of positive electrode sheet and battery: Same as in Example 1.

[0105] Example 5 The only difference between this embodiment and embodiment 4 is that the upper end of the main parameter range of the wet mixing coating process is used.

[0106] The specific preparation steps are as follows: In step (2), the reaction system is heated to 100°C and the reaction time is 4 hours.

[0107] In step (3), the inlet temperature of the spray dryer is 200°C and the outlet temperature is 100°C.

[0108] The rest is the same as in Example 4. The resulting composite lithium supplement is designated as S5.

[0109] Example 6 The difference between this embodiment and Embodiment 1 is that different inorganic lithium supplementing agents were used.

[0110] The specific differences are as follows: The inorganic lithium supplement was replaced with Li5FeO4 (pentalithium iron oxide, average particle size 5μm).

[0111] The remaining preparation process, parameters, and excipients are exactly the same as in Example 1. The resulting composite lithium supplement is designated as S6.

[0112] Example 7 The difference between this embodiment and Embodiment 1 is that a different organic lithium supplement was used.

[0113] The specific differences are as follows: Replace the organic lithium supplement with lithium phenyl sulfinate (Ph-SO2Li, where R is arylphenyl in the general formula).

[0114] The remaining preparation process, parameters, and excipients are exactly the same as in Example 1. The resulting composite lithium supplement is designated as S7.

[0115] Example 8 The difference between this embodiment and Embodiment 1 is that different conductive additives were used.

[0116] The specific differences are as follows: Replace the conductive additive with graphene.

[0117] The remaining preparation process, parameters, and excipients are exactly the same as in Example 1. The resulting composite lithium supplement is designated as S8.

[0118] Example 9 The difference between this embodiment and Embodiment 1 is that an inorganic lithium replenishing agent with a pre-coated carbon layer on the surface is used to support the limitations on the surface state of the inorganic lithium replenishing agent in the aforementioned embodiments.

[0119] The specific differences are as follows: The raw material used is Li2NiO2 (with a carbon content of about 0.5%) whose surface has been pre-coated with a nano-carbon layer, instead of the bare Li2NiO2 in Example 1.

[0120] The remaining preparation process (dry ball milling), parameters, and excipients are exactly the same as in Example 1. The resulting composite lithium supplement is designated as S9.

[0121] Example 10 The difference between this embodiment and Embodiment 1 is that an inorganic lithium replenishing agent doped with metal elements is used to support the limitations on element doping in the aforementioned embodiments.

[0122] The specific differences are as follows: The raw material selected is aluminum (Al) doped Li₂NiO₂ (chemical formula can be represented as Li₂Ni). 0.98 Al 0.02 O2), replacing the pure Li2NiO2 in Example 1.

[0123] The remaining preparation process, parameters, and excipients are exactly the same as in Example 1. The resulting composite lithium supplement is designated as S10.

[0124] Example 11 The difference between this embodiment and Embodiment 1 is that an organic lithium supplement containing a siloxane group is used to support the limitation in the foregoing embodiments that the R group is siloxane.

[0125] The specific differences are as follows: Replace the organic lithium supplement with lithium trimethylsilyl sulfinate ((CH3)3Si-SO2Li).

[0126] The remaining preparation process, parameters, and excipients are exactly the same as in Example 1. The resulting composite lithium supplement is designated as S11.

[0127] Comparative Example 1 This comparative example is used to compare the case without an organic coating layer.

[0128] 1. Preparation of lithium supplement: The inorganic lithium supplement Li₂NiO₂ was used directly without coating. No organic lithium supplement CF₃SO₂Li or dispersant was added.

[0129] To ensure a fair comparison, Li2NiO2 was simply physically mixed with the conductive additive CNT (without heating, at a low speed) to maintain a consistent conductive agent content.

[0130] The obtained sample is denoted as DS1.

[0131] 2. Preparation of positive electrode sheet and battery: Replace the composite lithium supplement S1 in Example 1 with DS1, and the remaining steps are the same.

[0132] Comparative Example 2 This comparative example is used to compare the case without an inorganic core (pure organic lithium supplement).

[0133] 1. Preparation of lithium supplement: Organic lithium supplement CF3SO2Li powder was used directly. Inorganic lithium supplement Li2NiO2 was not added.

[0134] Mix CF3SO2Li with the conductive additive CNT.

[0135] The obtained sample is denoted as DS2.

[0136] 2. Preparation of positive electrode sheet and battery: Replace the composite lithium supplement S1 in Example 1 with DS2, and the remaining steps are the same.

[0137] Comparative Example 3 This comparative example is used to compare the case of simple physical mixing (without forming an effective coating structure).

[0138] 1. Preparation of lithium supplement: The inorganic lithium supplement Li2NiO2, the organic lithium supplement CF3SO2Li, the dispersant PEG, and the conductive additive CNT were added to the mixer in the proportions of Example 1.

[0139] Mix at room temperature (25°C) at low speed (500 rpm) for 30 minutes without high-temperature ball milling (i.e., the "heating and film formation" step is missing, and the organic agent cannot be softened and coated by heat and high shear force).

[0140] The obtained sample is denoted as DS3.

[0141] 2. Preparation of positive electrode sheet and battery: Replace the composite lithium supplement S1 in Example 1 with DS3, and the remaining steps are the same.

[0142] Comparative Example 4 This comparative example is used to compare the case where no conductive additive is embedded in the coating layer.

[0143] 1. Preparation of lithium supplement: The composite lithium supplement was prepared according to the method in Example 1, but without adding the conductive additive CNT during the preparation process. That is, the resulting material is simply an organic-coated inorganic material.

[0144] In the subsequent preparation of the positive electrode slurry, an additional CNT of the same mass is added to the slurry (i.e., the conductive agent exists only in the electrode conductive network and is not pre-embedded in the lithium supplement coating layer).

[0145] The prepared lithium replenishment sample is designated as DS4.

[0146] 2. Preparation of positive electrode sheet and battery: Replace the composite lithium supplement S1 in Example 1 with DS4, and the remaining steps are the same.

[0147] Performance testing To verify the performance of the organic-inorganic composite lithium supplement provided by the present invention, the samples and batteries prepared in Examples 1-8 and Comparative Examples 1-4 were subjected to the following performance tests: 1. Environmental stability test (residual alkali growth rate): The prepared lithium supplement samples S1-S8 and DS1-DS4 were placed in a constant temperature and humidity chamber (temperature 25℃, relative humidity 50%) and exposed for 24 hours. The residual alkali content (calculated as the total amount of Li2CO3 and LiOH) on the sample surface before and after exposure was tested by acid-base titration, and the residual alkali growth rate was calculated.

[0148] Residual alkali growth rate = (residual alkali after storage - initial residual alkali) / initial residual alkali × 100%.

[0149] This indicator reflects the lithium supplement's resistance to water absorption and environmental stability.

[0150] 2. Battery electrochemical performance testing: (1) Initial Coulombic Efficiency (ICE): At 25°C, the battery was charged at a constant current rate of 0.1C to 4.2V, and then discharged at a constant current rate to 2.5V. The initial charge capacity and discharge capacity were recorded.

[0151] Initial coulombic efficiency = initial discharge capacity / initial charge capacity × 100%.

[0152] (2) Cyclic performance (capacity retention): At 25°C, charge and discharge cycles were performed at a rate of 1C / 1C within a voltage range of 2.5V-4.2V, and the discharge capacity after 200 cycles was recorded.

[0153] Capacity retention rate = Discharge capacity at 200th cycle / Initial discharge capacity × 100%.

[0154] 3. Test Result Analysis: Table 1. Performance test results of the examples and comparative examples

[0155] Results analysis: (1) Regarding environmental stability, compared with Comparative Example 1 (pure inorganic), the residual alkali growth rate of the sample from Examples 1-8 was significantly reduced (from 45.6% to below 3.5%). This indicates that the present invention effectively isolates moisture and air through the dense coating layer formed by the organic lithium supplement, solving the problem of inorganic lithium supplements easily absorbing water and failing.

[0156] Comparing Example 1 and Comparative Example 3 (simple physical mixing), the residual alkali growth rate of Example 1 (2.5%) was much lower than that of Comparative Example 3 (15.2%). This demonstrates that only through the specific dry heated ball milling or wet process of this invention can the effective coating of organic and inorganic materials be truly achieved; simple physical mixing cannot form a dense protective layer.

[0157] (2) Regarding electrochemical performance, the initial coulombic efficiency of the example groups was generally high (~89%). Although Comparative Example 2 (pure organic) had good stability, its initial efficiency was low (82.1%) due to the lack of high capacity and catalytic effect of the inorganic core and the poor conductivity of the organic material itself. The initial efficiency of Comparative Example 4 (without conductive agent in the coating layer) (85.8%) was also lower than that of Example 1, which proves that the embedding of conductive agent in the coating layer is crucial for improving reaction kinetics, reducing polarization, and ensuring that the lithium supplementer can fully exert its capacity.

[0158] Regarding cycle stability, Comparative Example 1 (pure inorganic) exhibited the worst cycle retention rate (82.3%). This is because the residues (transition metal oxides) from the decomposition of the inorganic lithium supplement catalyzed the decomposition of the electrolyte, thus disrupting interfacial stability. In contrast, the Example groups all maintained a retention rate above 91%, indicating that the sulfur-containing products generated from the decomposition of the organic lithium supplement formed a stable SEI film in situ, effectively suppressing side reactions and improving battery life.

[0159] (3) Regarding the modification of the inorganic core and the organic groups, for the synergistic effect of pre-coated carbon (Example 9), comparing Example 9 and Example 1, after using the inorganic core with pre-coated carbon, the initial coulombic efficiency increased to 90.2%, and the cycle retention rate increased to 94.5%. This indicates that the carbon layer on the surface of the inorganic core, together with the outer organic coating layer and conductive additives, forms a "through-and-through" dual conductive network, further reducing the interfacial impedance and strongly supporting the significant electrochemical performance improvement effect of the carbon coating layer limitation in the aforementioned embodiments.

[0160] Regarding elemental doping (Example 10), Example 10 uses an Al-doped inorganic core, and its cycle retention rate reaches the highest among all groups at 95.1%. This indicates that metal element doping effectively stabilizes the lattice structure of the inorganic lithium replenisher after deep delithiation. Combined with the protection of the organic coating layer, it achieves dual protection of structural stability and interface stability, fully supporting the technical features of metal doping in the aforementioned embodiments.

[0161] Regarding the film formation of silane groups (Example 11), Example 11 used an organolithium salt containing silane groups, which had a residual alkali growth rate as low as 2.0% and excellent cycle performance. This indicates that silane groups not only endow the material with better hydrophobicity, but their decomposition products may also form a tough interface film rich in Si-O bonds, further enhancing the protection of the cathode surface, thus strongly supporting the broad protection range and technical feasibility of the R group in the aforementioned embodiments.

[0162] In summary, the organic-inorganic composite lithium replenishing agent provided in the above embodiments, through core-shell structure design and specific preparation process, takes into account excellent environmental stability, high lithium replenishment efficiency and long cycle life, and has significant progress.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An organic-inorganic composite lithium supplement, characterized in that, Including inorganic lithium supplements and organic lithium supplements; The organic lithium supplement agent coats the surface of the inorganic lithium supplement agent to form a coating layer; The organic lithium supplement includes at least one of the compounds represented by the general formula R-SO2Li; Wherein, R is selected from any one of halogen, C1-C5 alkyl, C1-C5 alkoxy, aryl, heteroaryl, silyl or siloxane; the C1-C5 alkyl, C1-C5 alkoxy, aryl, heteroaryl, silyl or siloxane is unsubstituted or substituted by one or more substituents; the substituent is selected from halogen, cyano, alkyl, alkoxy, alkenyl or alkynyl; The organic-inorganic composite lithium supplement also includes a conductive additive; the conductive additive is dispersed in the coating layer and inside the coating layer.

2. The organic-inorganic composite lithium supplement as described in claim 1, characterized in that, The inorganic lithium supplement includes at least one of Li₂NiO₂ and Li₅FeO₄; and / or, The inorganic lithium supplement has a carbon coating or no coating on its surface; and / or, The inorganic lithium replenishing agent may be doped with a metal element or not; the metal element includes at least one of Mg, Al and Zr.

3. The organic-inorganic composite lithium supplement as described in claim 1, characterized in that, The conductive additive is selected from at least one of conductive carbon black, conductive graphite, carbon nanotubes, graphene, MXene, and carbon fiber; and / or, The organic-inorganic composite lithium supplement also includes a dispersant; the dispersant is selected from at least one of polyethylene glycol and sodium dodecylbenzenesulfonate.

4. A method for preparing an organic-inorganic composite lithium supplement as described in any one of claims 1-3, characterized in that, The preparation method includes dry mixing and coating or wet mixing and coating.

5. The preparation method of the organic-inorganic composite lithium supplement as described in claim 4, characterized in that, The dry coating process includes: Inorganic lithium supplement, organic lithium supplement and dispersant are mixed and stirred at 2000 rpm to 3000 rpm for 20 min to 30 min to obtain premixed material; Add a conductive additive to the premixed material, and ball mill at 300-400 rpm for 1-2 hours under vacuum or inert atmosphere. Then, heat to 50-100°C and ball mill at 500-800 rpm for 2-4 hours. Sieve to obtain the organic-inorganic composite lithium supplement; and / or, The wet-mix coating process includes: Organic lithium supplements and dispersants are dissolved in a solvent to form an organic lithium supplement solution; An inorganic lithium supplement and a conductive additive are added to the organic lithium supplement solution, dispersed, and then heated to 50℃~100℃ for 2h~4h to obtain a mixed solution; The mixture is spray-dried to obtain the organic-inorganic composite lithium supplement; wherein the inlet temperature of the spray dryer is 180℃~200℃ and the outlet temperature is 80℃~100℃.

6. A positive electrode sheet, characterized in that, It includes positive electrode active material, conductive agent, binder, and organic-inorganic composite lithium supplement as described in any one of claims 1-3.

7. The positive electrode sheet as described in claim 6, characterized in that, The mass ratio of the organic-inorganic composite lithium supplement to the positive electrode active material is (0.001~2):1; and / or, The positive electrode active material includes at least one of olivine-type structural materials, spinel-type structural materials, or layered oxide positive electrode materials; The general formula of the positive electrode active material includes LiM. z N 1-z PO4, Li 1+x Ni y Mn 2-x-y O4 or Li 1+a Ni b Co c M' 1-a-b-c O2; wherein M and N are one of Fe, Mn, Co and Ni respectively; M' is selected from at least one of Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Zn, Ga, Y, Zr, Nb, Mo, Sn, Ba and rare earth elements; 0≤z≤1, 0≤x≤0.5, 0≤y≤0.5, 0≤a≤0.5, 0≤b≤1, 0≤c≤1 and 0≤a+b+c≤1.

8. A lithium secondary battery, characterized in that, It includes a separator, an electrolyte, a negative electrode, and a positive electrode as described in claim 6 or 7.

9. An electrical appliance, characterized in that, Including the lithium secondary battery as described in claim 8.

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